The measurement of intrinsic viscosity is simple and inexpensive when compared with other measurements related to the polymer MW. However, it can be time consuming, even if modern semiautomatic instruments are used for that purpose. As mentioned in Chapter 1, measurements of intrinsic viscosity were historically important in establishing the concept of macromolecules [29]. The determination of the intrinsic viscosity of a polymer essentially requires the measurement of the flow time of a polymer solution through a glass capillary at different solution concentrations. A polymer solution passing through a capillary obeys the Poiseuille’s law for laminar flow through capillaries, which indicates that the pressure drop P is directly proportional to the viscosity η of the fluid [29, 30].